A. E. Feiring, Journal of Fluorine Chemistry, 13, 7-18 (1979) discloses the use of tantalum pentafluoride as a catalyst for the addition of hydrogen fluoride to tetra- and trichloroethane and related compounds. The catalyst is also useful in fluorine-chlorine exchange reactions. However, under the conditions of the batch experiments [HF/CCl.sub.2 .dbd.CCl.sub.2 =2.5, temperature=150.degree. C., reaction time=six hours] catalysts such as BF.sub.3, TaCl.sub.5, Ta.sub.2 O.sub.5, CoF.sub.3, V.sub.2 O.sub.5, ZrCl.sub.4, NbCl.sub.5, HgO, and WCl.sub.6 showed no catalytic activity for the addition of HF to tetrachloroethylene.
The use of tantalum pentafluoride as a catalyst for the addition of hydrogen fluoride to unsaturated compounds has been disclosed and claimed by Feiring in U.S. Pat. No. 4,258,255.
The use of dehydrating agents to prepare anhydrous TaF.sub.5 has been disclosed and claimed in Kim U.S. Pat. No. 4,124,692.
The need to provide an economically attractive process to produce highly fluorinated, hydrogen-containing alkanes useful as alternatives to current products for refrigerants, blowing agents, etc. has sparked interest in this area.
This invention provides a low cost process for the preparation of fluorinated alkanes made by catalyzed HF addition to olefins and/or fluorine for chlorine exchange on chlorinated alkanes using a system comprised of Ta.sub.2 O.sub.5 or Nb.sub.2 O.sub.5, a dehydrating agent(s), e.g., HOSO.sub.2 Cl (chlorosulfonic acid), and SOCl.sub.2 (thionyl chloride) and excess HF.